Peptidic vasopressin V1a receptor agonists, such as terlipressin, have recently (see e.g. O'Brian et al., Lancet 359 (9313):1209-10, Jun. 4, 2002) received increased attention for clinical use in treatment of critical care diseases and conditions, including shock of hypovolemic (e.g. hemorrhagic) or vasodilatory (e.g. septic) origin, bleeding esophageal varices (BEV), hepatorenal syndrome (HRS), cardiopulmonary resuscitation and anesthesia-induced hypotension. They have also been shown to have clinical use in the treatment of orthostatic hypotension, paracentesis-induced circulatory dysfunction, intra-operative blood loss and blood loss associated with burn débridement and epistaxis, and for treatment of various ocular diseases by increasing lacrimation/tear formation.
In treating critical care conditions it is highly desirable to control the arterial blood pressure, and the drug used is typically administered intravenously. Continuous intravenous drug infusion at increasing or decreasing rates is a practical means of providing the desired degree of control. The attainment of so-called “steady state” plasma concentrations of drug depends on the elimination half life of the drug infused. It is generally recognised that steady state plasma concentration is achieved after a period of time equivalent to three times the elimination half life of the drug. To be practical in a clinical setting the desired arterial blood pressure at the steady state should be attained in about two hours, preferably in one hour or less. V1a agonists with an elimination half life longer than 1 hour are therefore usually not considered useful for critical care treatment.
A disadvantage of terlipressin in many critical care situations is its long duration of action, which makes it difficult to titrate its effect as the disease state changes. The efficacy of terlipressin at the human V1a (hV1a) receptor also needs to be improved e.g. to allow lower dosages in general.
Also the compound known as F180 (cf. example 3 in U.S. Pat. No. 5,459,236) has an inconveniently long duration of action to be considered for the treatment of most critical care conditions.
Non-specific receptor agonist activity is the main disadvantage of other existing compounds, e.g. [Phe2,Orn8]OT (cf. example 1f in U.S. Pat. No. 3,352,843) and arginine-vasopressin (AVP). Activity at related receptors such as V1b, V2 and oxytocin (OT) receptors may potentially generate undesirable side effects and safety concerns. As an example, V2 receptor activation may induce antidiuresis (cf. desmopressin), release of coagulation/thrombolysis factors, and induce vasodilation/hypotension with reflex tachycardia. The latter side effect may also be induced by OT receptor agonist activity.
It is an objective of the present invention to provide compounds that are especially useful in the treatment of critical care conditions.